The electromagnetic spectrum encompasses radiation from gamma rays, x-rays, ultra violet, a thin region of visible light, infrared, terahertz waves, microwaves, and radio waves, which are all related and differentiated in the length of their wave (wavelength). All objects, as a function of their temperatures, emit a certain amount of radiation. For example, the higher an object's temperature, the more infrared radiation the object emits.
Thermal cameras have many applications, particularly when light and visibility are low. For example, thermal cameras have been used in military applications to locate human beings or other warm entities. Warm-blooded animals can also be monitored using thermographic imaging, especially nocturnal animals. Firefighters use thermal imaging to see through smoke, find people, and localize hotspots of fires. With thermal imaging, power line maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver at night.
Thermal cameras utilize an array of detector elements and each individual detector can have different gain and offset values that change with time, due to detector-to-detector variability in the fabrication process, sensor operating temperature, and the like. The difference in gain and offset values among detectors can produce fixed pattern noise in the image. Despite the progress made in the area of thermal cameras and thermographic imaging, there is a need in the art for improved methods of performing non-uniformity correction for thermal imagery.